Air rights are the property interest in the "space" above the earth's surface. Generally speaking, owning, or renting, land or a building includes the right to use and develop the space above the land without interference by others.
This legal concept is encoded in the Latin phrase Cuius est solum, eius est usque ad coelum et ad inferos ("Whoever owns the soil, it is theirs up to Heaven and down to Hell."), which appears in medieval Roman law and is credited to 13th-century glossator Accursius; it was notably popularized in common law in Commentaries on the Laws of England (1766) by William Blackstone; see origins of phrase for details.
Property rights defined by points on the ground were once believed to extend indefinitely upward. This notion remained unchallenged before air travel became popular in the early 20th century. To promote air transport, legislators established a public easement for transit at high altitudes, regardless of real estate ownership. Both the public easement in the space at these higher altitudes and landowner rights to the exclusive use of the airspace at lower altitudes have been well documented by the U.S. judiciary.
New technologies have again raised questions about ownership of "space" and the upward bounds of national sovereignty. With the advent of space travel above earth's atmosphere, the height at which national sovereignty extends and therefore nations can regulate transit is often debated.
In the United States, the Federal Aviation Administration (FAA) has the sole authority to regulate all "Navigable airspace", exclusively determining the rules and requirements for its use. Specifically, the Federal Aviation Act provides that: "The United States Government has exclusive sovereignty of airspace of the United States" and "A citizen of the United States has a public right of transit through the navigable airspace." The "navigable airspace" in which the public has a right of transit has been defined as "the airspace at or above the minimum altitudes of flight that includes the airspace needed to ensure safety in the takeoff and landing of aircraft." However, this does not authorize the United States Government to operate aircraft with impunity in regards to "substantial impairment" of private property, which constitutes a governmental taking requiring just compensation.
The exact altitude(s) at which the airspace over private land can become subject to "substantial impairment" is often debated. Case law in the past has used the height of 500 ft (150 m) in urban or suburban areas, and 360 ft (110 m) above the surface or tallest structure in rural areas as the demarcation of where impairment of property rights can occur. At those times this constituted the limits of "navigable airspace". However, the bulk of more recent decisions, which take precedent, hold that taking can occur regardless of if the flight occurred within navigable airspace or not and only impairment of property need be considered. This is especially important as some aircraft (manned and unmanned) now have no minimum flight altitudes making virtually all airspace "navigable".
The FAA is required to pay financial compensation to property owners when their property interests are taken for overflights (when federal government is the taking party ). Compensated landowners may then be required to waive any putative damages for interference with "air rights" in order to avoid lawsuits from future owners' nuisance claims against low flying aircraft. This is called a navigation or navigational easement. Congress has provided authority for the FAA to provide funds to purchase these easements near airports to accommodate planes taking off and landing.
The low cost of unmanned aerial vehicles (also called drones) in the 2000s re-raised legal questions regarding whose permission is required to fly at low altitudes; the landowner, the FAA or both. There has never been a direct challenge to the federal governments vesting of the right for citizens to travel though navigable airspace. As such, the status quo is only permission from the FAA (through regulation) is required. However, existing property rights over private property still allow for civil claims of taking when property use is "substantially impaired" by the use of the airspace. The FAA has also reiterated that it has sole authority to regulate this right. 
Railroads and air rights
Railroads were the first companies to realize the potential of making money from their air rights. A good example of this is Grand Central Terminal in New York City, where William J. Wilgus, chief engineer of the New York Central and Hudson River Railroad, devised a plan to earn profit from air rights. At first, the railroad simply constructed a platform above the rail yards to allow for the development of buildings overhead. By 1954, the railroad began to realize it could sell more air rights and Grand Central Terminal was proposed to be replaced by a 50-story tower. This is how the Pan Am Building came to be built next to the station, after public protest regarding the demolition of Grand Central Terminal. This approach has been used in Chicago since the construction of the Prudential Building in 1955 above active railroad tracks of the Illinois Central Railroad. In 2017, to the west of the Chicago River, River Point and 150 North Riverside were built above tracks leading to the Amtrak station.
Building on platforms over railroad tracks is still potentially very profitable. In the mid-2000s, New York's Metropolitan Transportation Authority (MTA) attempted to sell air rights to the New York Jets so that they could build the West Side Stadium over Manhattan's West Side Yard, near Penn Station, as part of the Hudson Yards Redevelopment. The Hudson Yards mega-development was eventually built over the rail yard. In Brooklyn, the Barclays Center and Pacific Park have been constructed over Atlantic Yards.
Roads and air rights
The city of Los Angeles funded a $100,000 feasibility study RFP in January 2007 to explore building a freeway cap park in Hollywood. The park would be built above US highway 101 and contain 24 acres (97,000 m2) of new parkland.
Air rights in development
The owner of the land has the exclusive development rights in the 'space' above his lands. Under common law, building a 'hangover' that breaks the vertical plane of a neighbor's property is a trespass and the property owner has the right to remove the offending structure. The airspace is property and retains developmental rights which can be sold or transferred. Thus in a dense downtown area, each building in the area may have the right to thirty-five stories of airspace above his own property. In one possible scenario, owners of an older building of only three stories high could make a great deal of money by selling their building and allowing a thirty-five-story skyscraper to be built in its place. In a different scenario, a skyscraper developer may purchase the unused airspace from an adjacent landowner in order to develop a broader building. In November 2005, Christ Church in New York sold its vertical development rights for a record $430 per square foot, making more than $30 million on the sale for the right to build in the space over its building.
- Paris Convention of 1919 (Convention for the Regulation of Aerial Navigation, Oct. 13, 1919, 11 L.N.T.S. 173) and the Pan American Convention on Commercial Aviation, U.S.-Cuba, Feb. 20, 1928, see 47 Stat. 1901)
- 49 U.S.C. 180, 49 U.S.C.A. 18, § 40103 "use of airspace"
- "49 U.S.C. 40103(a)(1)". Retrieved 2009-04-07.
- Pub.L. No. 85-726 https://www.govinfo.gov/content/pkg/STATUTE-72/pdf/STATUTE-72-Pg731.pdf
- Lacey v. United States 595 F.2d 614 (Fed. Cir. 1979)
- Causby v U.S. 75 F.262 Ct.Cl (1948)
- Branning v. United States 654 F.2d 88 (Fed. Cir. 1981) Held a taking occurred from air travel inside of navigable airspace (600') The present case is a case, as the court foresaw in Aaron v. United States, 160 Ct.Cl. at 301, 311 F.2d at 801, in which "the unavoidable damage [reduction of the highest and best use] to a person's property occasioned by [the noise created during] travel in the navigable air space [is] so severe as to amount to a practical destruction of it." This is a case of first impression in which the court may consider the altitude of the flights over the property, but must give primary consideration to the effect of aircraft noise where the Government itself has adopted and published standards of compatibility of use of the subjacent property. Since the subjacent property owner has suffered a diminution of the value of the property in this case, there has been a taking of an easement over and through the airspace subjacent the property of the plaintiff. It is abundantly clear that under the law established by Causby, Griggs, and Aaron a taking has occurred in this case.
- Griggs v. Allegheny County, 369 U.S. 84 It is argued that though there was a "taking," someone other than respondent was the takerthe airlines or the C. A. A. acting as an authorized representative of the United States. We think, however, that respondent, which was the promoter, owner, and lessor of the airport, was in these circumstances the one who took the air easement in the constitutional sense.
- 49 U.S.C § 40110
- Branning v. United States, 654 F.2d 88, 97-98 (Ct. Cl. 1981, Aaron v. United States, 311 F.2d 798, 801 Ct. Cl. (1963); Brown v United States 3 F.3d 1100 Ct Cl. (1996).
- "FAA press release".
- Gray, Christopher (October 11, 1998). "Grand Central Terminal; The 23-Story, Beaux-Arts 1913 Tower That Wasn't". The New York Times. Retrieved 2009-08-22.
- Fuller, Ernest (December 9, 1955). "Dedicate New Prudential 41 Story Building". Chicago Tribune. Retrieved September 7, 2017.
- McCown, James (September 4, 2002). "Boston Air Rights". Architecture Week. 113 (4).
- » Community-Wide Hollywood Central Park Meeting
- Bagli, Charles V. (November 30, 2005). "$430 a Square Foot, for Air? Only in New York Real Estate". The New York Times. Retrieved 2009-08-22.
- Types of development rights
- Air rights over Chicago's Merchandise Mart (an early example of air rights regulation)
- Can I declare a "no-flight zone" over my house?, The Straight Dope, 13 February 1998.
- New York City Air Rights Map
- Herships, Sally (November 18, 2013). "The Air Up There". Marketplace. Retrieved 18 November 2013. On the current state of New York City's air rights and their market.
- Troy A. Rule, Airspace and the Takings Clause, 90 Washington University Law Review 421 (2012).
Transferable Development Rights (TDR)
- Explanation of this concept from Eastern Michigan University
- Explanation of this concept from Ohio State University
- TDR "Field Guide"
- Transfer of Development Rights for Balanced Development from Lincoln Institute of Land